1. Field of the Invention
The invention relates to a device for regulating or limiting at least one temperature value or one temperature range of radiant-heating or contact-heating bodies of electrical cooking appliances in conjunction with hobs consisting of metal, glass ceramic or the like, in which, in order to regulate or limit the temperature of the heating body or heating bodies, between the heating body or heating bodies and the hob is arranged at least one temperature sensor having a bar of high thermal expansion, the said bar being arranged in a tube of low thermal expansion, one end of the bar being connected to a contact system serving for regulating or limiting the temperature of the heating body.
2. Description of the Related Art
In the device of the type mentioned, the temperature is regulated or limited particularly by utilizing the temperature-related axial movement of the bar-shaped temperature sensor to actuate the contact system, specifically in such a way that the heating circuit is cut in at a specific temperature and is cut out again at a specific higher temperature.
The tube surrounding the bar consists of a material resistant to high temperatures and having a low coefficient of thermal expansion and retains the bar against the axially exerted resistance of a helical spring, with the result that the tube is under axial compressive stress.
This leads to difficulties, especially during assembly, since a pivoting of the contact housing relative to the temperature sensor, that is to say the bar/tube arrangement, can occur thereby.
However, this pivoting movement often causes the tube formed from quartz glass to splinter off at the end located on the same side as the contact housing and consequently the set regulating temperature to be put out of adjustment.
Acording to U.S. Patent Specification No. 4,215,332, there is also a known device of this type, in which the quartz-glass tube is inserted into a metal mounting which rests on a dome-shaped bulge. However, if the gas tube is tilted, it can splinter off because of the tolerances between the glass tube and the metal mounting. Furthermore, lubrication has to be carried out because of the high friction values between the metal mountings and the bulge likewise formed from metal. If the friction values are too high as a result of a lack of lubrication, a breakage of the tube is often unavoidable.